Explained: Nanowires and nanotubes
Nanowires and nanotubes, slender structures that are only a few billionths of a meter in diameter but many thousands or millions of times longer, have become hot materials in recent years. They exist in many forms — made of metals, semiconductors, insulators and organic compounds — and are being studied for use in electronics, energy conversion, optics and chemical sensing, among other fields. This Scanning Electron Microscope image shows an array of nanowires. Photo: Kristian Molhave/Opensource Handbook of Nanoscience and Nanotechnology The initial discovery of carbon nanotubes — tiny tubes of pure carbon, essentially sheets of graphene rolled up unto a cylinder — is generally credited to a paper published in 1991 by the Japanese physicist Sumio Ijima (although some forms of carbon nanotubes had been observed earlier). Almost immediately, there was an explosion of interest in this exotic form of a commonplace material. Nanowires — solid crystalline fibers, rather than hollow...